The objective of this study is to estimate the maximum capital cost of a marine energy project such that electricity is generated at a target levelised cost of electricity. A capital cost is evaluated for alternative wave energy technologies at a particular site. The approach taken is to employ the standard Net Present Value method to quantify the budget that is available for all expenditures that can not be quantified at the present stage of development. A positive net present value is typically required to justify investment in a marine energy project. Positive NPV is only obtained if the present value of all revenues is greater than the present value of all expenditures over the project life. Initially, project revenue is estimated based on site resource and device performance. Subsequently, the present value of each of the expenditures associated with the site and technology are subtracted to estimate the budget available for outstanding capital costs. Several idealised devices are considered at eight different wave sites to quantify the number of devices in a project and hence estimate the capital cost per wave device that would result in a positive Net Present Value. The idealised devices considered are types of heaving point absorber. One of the device types is assumed to operate at the point absorber limit in all wave conditions that occur at each site. This limit is dictated by the resource not the device dimensions and so represents the maximum power output that could be achieved by a heaving device. Application of this method to a range of sites would allow identification of the maximum device cost for each site so represents a capital cost ‘budget’. If applied to a technology at an early stage of development it can be used as a method of identifying the market size for different technologies.